Ten percent of the U.S. population will develop kidney stones. Three million Americans seek treatment each year, and total treatment cost is over $2B. Initial success rates range from ~70% to greater than 90% depending on the type of treatment performed, but stones will recur in half the patients within 5 years. Follow- up surgical management of stones is complex and individualized but expends significant resources, creates additional discomfort and can expose the patient to X-rays many times. Small stone fragments in the renal pelvis have a good chance of passing naturally, but fragments located in the lower calyces are more likely to remain and become problematic. We have developed a handheld pulsed-ultrasound device to non-invasively expel stone fragments (or small stones) from the kidney. We have also developed a unique ultrasound imaging method to dramatically enhance the visualization of kidney stones, which provides a safe alternative to the ionizing radiation of plane X-ray and computerized tomography (CT). A prototype device has been engineered from a commercially available diagnostic ultrasound imager and probe. Preliminary results in animal models show we can localize and safely repositioning stones from the lower calyx to the ureteropelvic juncture (UPJ) in less than 5 minutes, a procedure that could easily be completed during an office visit. The objective of this proposal using human subjects is to assess the ability of this device to reposition stone fragments. We will first measure, imaging accuracy of enhanced ultrasound localization compared to CT as the gold standard. In partnership with a regulatory consultant, we will prepare an application to the U.S. Food and Drug Administration (FDA) for an Investigational Device Exemption (IDE) to test the therapeutic strategy of repositioning stones in human subjects. The long-term goal is to provide urologists with a new non-invasive surgical option to clear stone fragments and small stones from the kidney. This device would be used to clear residual fragments remaining after shock wave lithotripsy (or invasive stone removal such as ureteroscopy), and could be a means to prophylactically expel small stones from the kidney before they become symptomatic. This stone repositioning device and its complementary stone imaging methodology have the potential to deliver safer, more effective treatments and significantly lower healthcare costs.